Perceived sharpness of displayed images is an important parameter in defining picture quality. Many devices utilize sharpness enhancement to optimize visual display of image data. There are several techniques for improving sharpness. The conventional methods of sharpness enhancement typically assume that received image data relates to full spectrum, for example data satisfying the Nyquist frequency. However, in many cases received image data may be sub-optimal. For example, one cause of spectrum reduction in image data may be due to upscaling of lower definition video sources (e.g., 480 p resolution such as video format) to a high-definition format. As a result, sharpness enhancement performed on the image data without knowledge of the incoming image data spectrum can render sharpness enhancement of the image data ineffective. The conventional methods and devices for image enhancement, however, do not address spectrum of the input image data.
For display devices in particular, such as digital televisions, sharpness enhancement has become an important issue. Quite often, standard definition (SD) video and television (SDTV) sources may be upscaled and broadcast as high definition (HD) programming. Many of the conventional techniques apply static sharpness settings usually based on an assumption that signal quality matches picture resolution and thus, disregard upscaled image data. In this particular case, the conventional techniques for sharpness enhancement based on the received imaged data will not produce the desired effect. Conventional techniques of contrast enhancement further do not address the presence of artifacts in broadcast image streams, nor the presence of HD graphics (e.g., logos) overlaid on broadcast image data.
Thus, there is a need in the art for systems and methods of spectrum estimation of image data and determination of sharpness enhancement control parameters.